This invention relates to a novel method for the manufacture of single crystals of .beta.-PbO.sub.2 and to the slender single crystals possessed of a metallic gloss which are produced by the said method.
Lead dioxide is generally known as serving the purpose an anodically active substance in lead storage batteries. It also finds utility in various electronic materials.
For lead dioxide to be effectively put to such uses, it is prerequisite that the basic physical properties thereof be accurately determined in advance. For this purpose, lead dioxide is required to be in the form of single crystals. If this compound is put to the uses mentioned above in the form of single crystals, then there can be obtained products with notably improved quality. Further, availability of the compound in the form of single crystals can be expected to encourage development of new uses.
The lead dioxide which is usually available is a powdery substance produced by a chemical or electrolytic process or a polycrystalline substance formed by electrodeposition. It is, therefore, not suitable for the determination of basic physical properties.
The considerable discrepancy among the test results which have been reported in the past is attributable to the use of such unsuitable lead dioxide.
Nothing has so far been reported as to the manufacture of single crystals of lead dioxide. In the specification of German Pat. (DRP 697068), there is a description to the effect that PbO or Pb(OH).sub.2 as a starting material is treated in an aqueous alkali solution under the pressure of air or oxygen. This treatment is not directed to the production of single crystals of PbO.sub.2. When the present inventors actually tried this treatment by following the procedure described in the preferred embodiments of said German patent, the product obtained was either Pb.sub.3 O.sub.4 or powdery PbO.sub.2 having a low degree of crystallinity. They have thus confirmed that the method disclosed therein cannot produce single crystals of PbO.sub.2 aimed at by the present invention.
An object of this invention is to provide an easy and commercially feasible method for the manufacture of single crystals of .beta.-PbO.sub.2.
Another object of this invention is to provide a method for the manufacture of single crystals of .beta.-PbO.sub.2, which method is such that the raw material is readily available and the product is obtained in high yields.
Still another object of this invention is to provide a method for the manufacture of single crystals of .beta.-PbO.sub.2 uniform in size.
Yet another object of this invention is to provide slender single crystals of .beta.-PbO.sub.2.